The present invention relates to a wire bonding apparatus and, more particularly, to a wire bonding apparatus which can shape the loop of a bonding wire into a desired shape and stabilize the shape of the loop.
As the integration of semiconductor integrated circuits becomes higher, the number of external leads and pins of the semiconductor integrated circuit devices also becomes greater; however, the number of the electrode pads or wire bonding regions and electrically conductive leads disposed around a chip on which the semiconductor devices are formed, is restricted by virtue of the size and shape of the chip or the size and shape of the package. Consequently, there is a certain limit to the increase of the number of pins and, at present, for a chip size of 12.times.12 mm, the number of pins is at most 208.
Attempts have been made to increase the number of pins of semiconductor integrated devices by forming electrode pads as planar shaped parallelograms so as to reduce a pitch between adjacent pads; however, a disadvantage resides in the fact that such attempts are inevitably restricted by the working properties and reliability of the wire bonding when the wire is bonded to the pads.
In accordance with another proposal, the electrode pads and leads to be formed on the chip are arranged in a zig zag pattern so as to substantially decrease the pad pitch; however, a disadvantage of this proposal resides in the fact that, if the pad pitch is reduced, the adjacent wires come closer to each other and eventually may be brought into contact thereby resulting in the development of short circuits. Because of the shape of the loop of the bonding wire formed between the electrode pad or a first bonding region and a lead or second bonding region in the wire bonding apparatus is primarily determined by the control of the vertical movement of the wire connecting tool of the wire bonding apparatus, that is, by a Z axis control, and by the wire hardness, the wire bonding apparatus is less able to change the shape of the loop and the stability of the loop itself is relatively low thereby resulting in the short circuit problem noted above.